abaddon
by Victoria LeRoux
Summary: It started with a sneeze and ended with poison. Natasha and Steve's adventures during Iron Man 3. Featuring Natasha Romanov, who's comfortable stabbing people but not discussing feelings, and Steve Rogers, who may have been poisoned.


2013 Secret Santa fic for red_b_rackham. Posted a full year after originally written. Go figure. This was written before Cap2, but I figured we needed some more Natasha/Steve adventures on this site anyway. Does anyone else find it irritating how Avengers/Captain America/all the other MCU movies are in a different category?

Summary: It started with a sneeze and ended with poison. Natasha and Steve's adventures during Iron Man 3. Featuring Natasha Romanov, who's comfortable stabbing people but not discussing feelings, and Steve Rogers, who may have been poisoned.

Title inspired by the verse: _"_Shall thy loving kindness be declared in the grave or thy faithfulness in destruction?"_. _

* * *

abaddon

* * *

Natasha's not entirely sure how it started, but what she is aware of is this:

It starts with a sneeze.

A sneeze from Steve, to be perfectly clear, one abrupt and ill-timed enough to make them both flinch with the severity of the noise. For a moment, they just stare at one another in complete, perfect silence.

"Sorry," Steve apologizes after a brief confused pause.

Natasha doesn't reply, not at first. Instead she weighs the situation carefully in her mind and, ignoring his cursory apology, says, "I didn't think it possible for you to sicken."

Steve looks, if not more confused, than at least as perplexed as Natasha herself. They don't have to worry about being overheard in the small but noisy café, but she can tell he's choosing his words with care when he tells her, "Not since…" he waves a hand about, seeming to waver between anxious and confused. Like him, he seems to decide on both because rather than continue he finishes with a flat, "you know."

Natasha's perfectly aware, and that's perhaps what worries her the most, but it won't help either of them if she voices her concerns. Instead, she simply levels him a coy look, letting a small smile touch her lips as she senses the target's eyes fall on her.

"That doesn't work on me, not anymore," he tells her, but matches her body posture as she leans across the table. She covers his hands with her own, looking up at him through her lashes.

"Any other symptoms?" she asks, tapping his cool hands with one pinky. Her smile doesn't falter as his look turns thoughtful and introspective.

"A little congestion, nothing more," he admits. "The mission will be fine."

She doesn't want to take his word on it, but she's well aware Fury chose this mission specifically for the pair of them. If they call it off now… they're aware of the ramifications of the WSC taking a closer look at Captain America's other undercover missions. Better to give Fury an ironclad, sparkling example to wave in front of the bureaucrats.

Instead of calling him on stretching the truth, she flops back against the booth and crosses her arms. For a moment, she lets her foot tap against the tiled floor of the cozy café, then she shrugs.

"I suppose we should have anticipated this," she tells him rather thoughtfully, and at his suspicious look, continues, "After all, this vacation was going entirely too well."

It startles a laugh out of him, at least, and Natasha's content to allow him to believe her remark was meant to be made in levity. But as she used the window beside her to watch their mark disappear into the café's back room, she was well aware the mission had been running without a hitch.

* * *

At first, Natasha doesn't give herself time to worry. There seems to be enough to keep her preoccupied for the remainder of the day – a bug drop in the target's hideout, a drop by the bar in the evening where she finds Steve chatting cheerfully with the target's girlfriend, a run to the convenience store for some Tylenol, and on second thought, Sudafed – so she doesn't remember to worry about Steve's innocuous sneeze until later.

It's Natasha's turn on watch and it's not until Steve lets off a small cough around midnight that she remembers her earlier concerns. Casting a quick glance outside the window that they've been using to spy on their target's apartment, she crosses the loft rapidly to drop down by his side.

His pulse is steady against her fingers and she scarcely hears any sign of congestion before she backs away, reassured. Likely, he's just reacting to the different altitude or some other probable event.

Natasha watches the street outside, mind whirring away at a price too rapid for boredom. She lets Rogers sleep through his shift, still consumed by the strange foreboding a simple cold had thrust upon her. While it certainly seemed odd for him to fall ill, it could simply mean he'd come in contact with a particularly virulent strain and he'd suffer no serious sickness as his body fought it off.

It's illogical for her to worry, she decides at last. And even if it isn't, fretting about something she can't change would only distract her from their mission at hand.

Gather intel, place it in a drop site for a local agent, and meet at the extraction point in less than a week. On paper, it had seemed – and still did appear – simple enough.

But as Steve shifts restlessly upon his bed, another small cough rising out of his lungs as he rolls from his back to his side, Natasha can't help but think about everything that can go wrong.

* * *

In the morning, as Steve levels a glare at her, she finds herself torn between amusement and anxiety. Eventually, as Steve croaks out a sullen, "You let me sleep through my shift" she decides both emotions are warranted.

Steve practically bowls her over in his eagerness to reach the not-so-affectionately dubbed "watch chair" where he can stare out the window and watch their target prepare for the day. Natasha doesn't comment on the fact that he nearly trips over his own feet as he crosses the even ground.

"You look like shit," she tells him with as much affection as she'll ever allow, and ignores his almost-huff. His throat's starting to sound too clogged for the noise to have much emphasis and Natasha's been immune to them since the team's inception for his desired effect to take place.

"What's on today's itinerary?" he asks her, voice cracking as he forces the words out.

Natasha looks at the dark circles under his eyes, the way his hands slightly shake as she hands him a hot mug of tea, and pointedly hands him a tissue.

"You're staying here," she orders, and when it appears as though he's about to protest, "I need to tail him today, and I can't do that with you sneezing behind me."

She doesn't give him any details – if she gives her suspicions voice, all she'll be doing is giving him fodder to insist he follow her. Natasha meets his gaze squarely, a horde of argument at her lips to forestall his protests.

"What time can I expect you back?" Steve says with a slight snuffle. Natasha feels a vague sense of victory at his acquiesce, but doesn't pause to gloat.

"Sometime after the bar closes," she admits slowly. "Three, maybe four."

"That late?"

She gives him a sharp smile, "Don't wait up. If I'm not back-"

"I'll come to the bar," he tells her. Natasha looks at him critically, scanning him for any sign of illness beyond his hoarse voice and clogged nose.

She doesn't find it, but shakes her head anyway. "-don't leave the room. You're still a probationary agent, Rogers."

A disgruntled look crosses his face briefly – whether it's at Natasha's stubbornness or her reminder of the title Fury had shoved upon him, she's not sure. She doesn't particularly care either way, so long as he obeys. Natasha looks at him pointedly, waiting until he jerks his head in a semblance of a nod. In return, she gives him a tight-lipped, slightly amused smile.

"There's some soup under the sink," she tells him curtly, then raises a brow. "Don't worry about keeping watch. Go sleep until I get back."

He mumbles agreement, getting blearily up from the chair and heading slowly back to the bed. Natasha affords herself another small smile - she would have never expected an ill Steve Rogers to be a cranky Steve Rogers.

Thoughts dwelling on that detail with amusement, Natasha departs as swiftly as she can. Thankfully, she's gone before he can point out that she hasn't slept in over a day.

* * *

Natasha's used to working alone. Before SHIELD, that's how she preferred to work. Even after joining SHIELD, her interest lay in missions where she needed no backup, where a partner was a meaningless term. A Black Widow is a solitary creature and the title is one Natasha wears with pride. Except now, after Barton, after the Avengers Initiative, even after spending three days with Rogers at her side, she's adjusted to having a sidekick without realizing it.

The situation's an interesting case study, but uncomfortable for her to come to terms with. Without any choice in her situation, she's grown used to – perhaps even fond of – having a partner she can depend upon. Except the worry, the need to look after another beside herself – Natasha fears that is something she can never become accustomed to.

Idly, Natasha takes a small sip of her beer, and when the drinker next to her turns away, swaps her nearly full drink for his almost empty one. She doesn't take another gulp but instead watches the occupants of the bar mingle. Her eyes fall upon the target as he tells his girlfriend a joke, and the couple laugh today. Natasha narrows her eyes slightly, keeping careful note of their interactions and wondering what Steve would say of it.

Her phone rings, jerking her out of her contemplation. With a small curse, she slips it on silent, eyes breaking from the targets to look at her drink. Natasha taps her fingers gently across the counter, ruminating on the couple before she checks her watch.

Ten forty-five. Far too early for the pair to call it a night – Natasha hasn't seen them leave the bar before one in the week they're been tailing them. Even that was an early night for them. Natasha wavers briefly, well aware of her orders to observe only. Natasha lets her eyes fall on her tapping fingers before she looks at the pair once more. As the target gives a full laugh, calling for another drink, his girlfriend snags his almost empty one to finish it off.

A perfectly normal scene, Natasha knows. Except… Natasha turns away with a frown, rubbing the side of her neck. Her instincts growl a soft warning to her and Natasha's spent enough time living by her wits that she can't allow herself to ignore them. Abruptly, she stands, sliding a ten to the bartender as she turns away from the couple.

Ten-fifty. Plenty of time to break into the target's house, snoop around, and leave before their return.

* * *

Natasha creeps back into the apartment at nine-fifteen the next morning, steps silent and steady as she slips through the door. Their small suite is silent and for a moment, the vast and empty feeling Natasha feels upon crossing the threshold forces her to pause.

"Steve?" she calls softly, a coaxing quality to her voice. No response comes her way, and she frowns, the weight of her stolen pendrive heavy in her purse. "Steve?"

Cautiously Natasha moves across the small kitchen to the door leading to the bedroom. With one hand, she slowly pushes the door open. The door's slight squeak punctuates the silence as Natasha enters the room. She doesn't call out his name again, instead choosing to remain silent as she crosses to where she can see a huddle of blankets in the back corner.

Her worry spikes as she pulls at the edge of the comforter and reveals the edge of his head. Her nose wrinkles as she catches, for the first time, the smell of the bucket he must have placed beside him after she left. There's a gun on the ground beside her and she slides it into her ankle holster with one hand, leaving the other to brush against his forehead.

It's hot, hotter than she'd expected. Natasha frowns at Steve, sitting back on her heels as she takes in his utter lack of reaction. She's seen him roused from the deepest of sleep at one of her quietest steps before, and for him to not even react to a touch…

She leaves the room swiftly, pulling her phone from her pocket quickly. The movement jogs her memory of the night before and Natasha narrows her eyes as she spies Steve's number as her single missed call. However, she dials the phone rapidly, moving aimlessly through the kitchen as she does so.

"Romanov," Hill's cool voice provides welcome relief. Natasha's not accustomed to demanding help from SHIELD, but Steve's predicament's left her anxious and weary.

"Rogers is ill," Natasha reports. "We gathered all the required intel already so I'm requesting an immediate evacuation."

There's a long pause from Hill before she says, "Rogers doesn't get sick."

"I'm aware," if Natasha's voice borders on insubordination, Hill doesn't remark on it. Natasha's pacing brings her to the sink once more, so she turns on her heel to head for the door. Nine steps one direction, then she has to turn and move back to her previous location. "Is it possible the serum's ceased to be effectual?"

The thought's just occurred to her, and it's a dark one. Idly, Natasha finds herself drumming her fingers against her thigh and forces her body to still. Pacing and fidgeting? She can't help but scold herself for allowing herself to show such common tells, even if no one is present to see her.

"We've run tests," Hill's tone effectually closes the argument. "The likelihood of the serum dissipating is…" An uncertain pause, as though Hill has never actually considered the possibility before despite her earlier claims. "Improbable at best."

"He needs immediate medical treatment," Natasha drops the subject entirely, instead choosing to focus on what she can have some effect on. "How soon can we be pulled from the mission?"

Another pause from Hill. Natasha's beginning to wonder if a single thing will go right today, and concludes that the answer is probably not when Hill tells her, "Not before the scheduled extraction date. We've had a situation develop."

"Agent Hill-" Natasha isn't sure what she's going to say, finds herself suddenly at a loss. Being unaware of which strings to pull leaves her floundering and it's a situation Natasha would prefer to never find herself in again.

"It's Stark," Hill tells her. "He's… presumed dead."

For a heartbeat, Natasha isn't entirely sure she heard Hill correctly. Then Hill's words hit her and she feels a violent shiver ripple through her spine. The two sentences don't connect. Instead, they clash discordantly together, a cacophony of impossibilities in five simple words.

Then she thinks about Rogers in the room next door, dead to the world, and remembers it's Christmas, a time of improbabilities. As Natasha pulls out another can of soup, she reasons that their lifestyles don't exactly lend to joyful endings.

"How?" Natasha asks, and that single word promises retribution. For a moment, she just needs a target that she can focus her rage on, a scapegoat for her emotions.

"The Mandarin," Hill tells her simply.

Natasha nearly snaps the mug she just pulled out from the cupboard and takes a steadying breath. "I downloaded the contents of the target's computer," she tells Hill slowly. "If I find the information we're looking for-"

Natasha stops, not entirely sure what she's requesting. But Hill knows, just as she always has. "You have permission to do as you see fit," Hill tells her. "Just keep local involvement to a minimum."

"Yes sir," Natasha's voice falls in the too-silent apartment, echoing in the stillness. A small scuffle from behind her makes her whirl, hand falling to her closest knife.

The sight of Rogers staring blearily at her makes her chest abruptly lighten, and Natasha ends her conversation with Hill using a few rushed words.

"I waited," Steve's voice edges on petulance briefly before settling into confusion. "Nat, I thought-"

Natasha winces at the creaky quality of Steve's voice and gestures to a chair. "I got trapped in the target's house," she explains as the microwave gives off a small ding. She turns away and can hear Steve's chair scrape across the floor as he sits heavily. With a frown, she pours the soup into a pair of mugs and hands him one. "I wanted to get some intel while the target was at the bar."

He frowns at her, with the same team leader glower she recalls the Winter Soldier using on missions when she did something he particularly disapproved of. "You should have taken me," Steve's voice cracks and almost disappears midway through the sentence.

Natasha returns the same frown he'd just wielded against her as he sneezes. "You look feverish," she ignores his comment pointedly, instead placing her hand against his forehead like she can remember her mother doing when she was a child. "Are you still nauseous?" she asks, remembering the bucket she'd seen earlier.

"A bit," Steve admits. "But I'm fine."

Natasha reaches across the table and steadies his shaking hands as he lifts his mug. "Of course you are," she tells him dryly. "Aching at all?"

A noncommittal murmur is her answer.

"Go," she orders, taking the soup from his hands. "Sleep."

Steve looks at her uncertainly. "Natasha," he says, and for a moment Natasha feel a prickle of irrational anger at his insistence upon calling her by her first name. She doesn't want to feel close to him, to the rest of the team. She doesn't want to feel obliged and attached to them. "I haven't been sick since before they gave me the serum."

But damn it, she does.

"It's probably just a virus you're fighting off," she lies with a concerned look. For now, she lets her suspicions remain exactly that – gut feelings. "An especially virulent one, or something similar."

He doesn't comment on her reciting her earlier statement once more and he doesn't call her on her lie. Natasha wishes that she could simply give credit to her skill as a spy but knows he's likely too sick to care.

As Steve stumbles to the single bedroom, looking utterly exhausted, Natasha slips the pendrive holding the contents of the target's computer into her hand. Surely, she reasons, somewhere in the midst of the data she'll find the information she's looking for. Natasha inhales, a long grounding breath before she lets it out in a puff of air. Grabbing the laptop Stark had gifted her for what he thought was her last birthday - but in actuality, was only Natalie Rushman's - she plugged in the pendrive.

It's not until Natasha takes a sip of her cooled soup that she realizes she never mentioned Stark to Steve at all.

* * *

Natasha's in the midst of reading an engaging file about experiments the target was running under orders on human test subjects when she hears a crash from the other room.

In a flash, she's on her feet and in the bedroom, one hand clenching tightly on her knife. It takes her a moment to realize the complete lack of threat and slowly allow herself to relax.

"Natasha," Steve says, looking frantic. "We have to help Tony."

It feels as though ice has replaced blood in her veins as Natasha glides forward to where Steve's trying to pick himself off the ground. This utter uncertainty on how to cope with being a team member - does she tell him the truth? Does she tell him Stark's dead? Or is it better to let him think Tony's perfectly safe? - is beginning to wear on her nerves. She hates the sensation of being caught in events beyond her control.

"Steve," she says desperately. "Tony-"

Steve uses the bedframe to pull himself up, wild eyes searching the room for something she can't decipher. "Natasha," Steve continues, voice bordering on harsh. "We can't let him do this."

"Tony's fine, Steve," Natasha tells him, the lie falling like honey from her lips.

"No," Steve replies, falling as he tries to take a step forward. Natasha catches him, his deadweight a surprise to her. Weakly, he flails against her, knocking the breath out of her as his elbow jabs into her stomach. Natasha sinks to the floor in a controlled collapse, bringing Steve to the ground with her. His skin almost burns to the touch, and its hotter against her skin than she would expect.

Natasha can almost hear the tick of the clock winding down.

"Yes," she tells Steve fiercely. The intensity of her voice surprises even her. "Tony is fine."

Rogers looks at her, the confusion in his eyes apparent as he searches her for… something. She isn't entirely sure what. Except it seems that whatever he's looking for, he finds, as he says, "Are you sure?"

Natasha thinks of Hill's voice, thinks of the ice in her blood and gives Steve a small smile. "I promise."

* * *

Her search through the files only grows faster. Natasha works at a frantic pace, tearing through the information at a speed she's never quite attained before. She can feel a palpable race against time beginning and pushes herself.

She's reached the point where she's too tired to even contemplate sleep. She can feel her body giving up protesting the lack of sleep and her mental state reach the point where nothing matters but the mission. Natasha's given up entirely on keeping an eye on both the target and Steve – now, she sits at the foot of the bed, laptop on her knees as she skims through the files on human experimentation.

She finds what she's looking for in the midst of a folder labelled Extremis. Natasha's never heard of it, but that doesn't mean much to her. There's a lot she never hears about and she's come to accept it.

There's only three files in the folder, but it's enough to make her know she's found what she's looking for.

Supersoldier and subjects and failures and competition – the words begin to blur together until Natasha's barely reading the information before she compartmentalizes it. Behind her, she can hear Steve's breaths growing fainter until they're scarcely audible. His wheezes occasionally shake the bed and Natasha winces with each cough.

It's when his coughs begin to tint red that she thinks she has enough information.

"Rogers," she says sharply, voice cutting through the silence of the apartment. She grabs his elbow and finds herself blocking a clumsy blow. "Rogers."

Slowly he awakens, each movement sluggish and heavy as he tries to roll onto his back. As the frequency of his coughing increases, Natasha helps him sit upright.

"Rogers," she tells him quietly. "Steve, I need to leave."

He looks at her, still hazy with sleep and incomprehension. "Nat?" he mumbles, voice thick with pain and cheeks flaming.

"Steve, I'll be back soon," she keeps her voice low and soothing. "I won't be long. I just need to pick up your medicine."

"'M'kay," he mumbles, eyes already sliding shut.

"I need you to stay awake while I'm gone," Natasha orders. He responds automatically to the authoritative tone, eyes snapping open before they begin to flutter closed. Natasha shoves a gun into his hand, helping him close his fingers around it. "The safety's on. If anyone comes through the door without warning you, I want you to shoot them. Can you do that for me?"

Natasha doesn't do comforting or uncertain well, she decides. But something in her voice makes Steve pay attention, for he gives her a slow nod. There's still confusion in his eyes, but he seems to have restored enough clarity for her to depart.

Natasha checks her guns, knives, shocks before leaving. Her laptop she slides under Steve's pillow, reasoning that if she lost Steve the remainder of her information would be moot as well. "I'll be back soon," she promises from the doorway, looking down on his listing form.

He nods at her, rubbing at his head dizzily. "I know," he tells her simply.

The faith in his statement shakes her and Natasha can't help but hope that she won't let him down.

* * *

"What did you do to him," Natasha snarls, gun pressed against her target's throat. He's terrified, shaking with fright as he meets her eyes.

"N-nothing!" he squeaks in the face of Natasha's fury.

"Extremis," she says simply, burrowing her smoldering rage within her. The switch from blistering anger to cool calculation unnerves him – his shaking only increases as he meets her eyes. "What is it?"

"It's-It's Killian's project. He wants to create more superhumans. I don't know why – he's been giving it to soldiers!" the man would have moved back if he wasn't already backed into the already wilting Christmas tree in the corner of his office. Natasha presses closer into his personal space, her gun lightly tracing the outline of his throat.

"Look," he says frantically, eyes wide with fear. "I didn't have anything to do with it. It was all her – she promised it would be all we needed to set us up for life. I just went along with the ride."

Natasha can see the truth in his eyes, but she wonders if he truly believes that his actions are excused. Slowly, she lets her gaze flicker away from him.

As he makes a wild lunge for his own gun, Natasha wonders if her actions were ever as desperate, ever as obvious as his. Another day, one when Natasha wasn't watching her already small list of allies dwindle down one by one, she may have let him believe he had a chance of success. Except today, Natasha is in no mood for mercy.

The Black Widow strikes, swift and sure.

* * *

Subtlety a foregone conclusion, Natasha invades the café. As she enters, she allows the door to slam against the wall, startling the three patrons.

Her eyes examine the café, watch the target's girlfriend take her in as the woman's face rapidly pales. "Out," Natasha orders, the word lingering in the café's sudden silence. The patrons don't hesitate in rushing out of the door.

Natasha remembers these days, the days where the Widow wasn't just a spy. She's done this before, she knows with shocking clarity. Before today, she never needed to remember the feeling of walking into a room and feeling its occupants fall silent, stricken with terror. She'd given up that part of herself, the deadly whirlwind of rage and destruction, when she'd joined SHIELD.

Now, it seems as though she discovers it once again all too easily.

Natasha crosses the space slowly, deliberately, each step echoing as her heel hit the ground. Every movement lithe and graceful, she stops when she's across the counter from what she had once believed to be a guileless woman.

"I believe you have something I'm looking for," Natasha says simply.

The woman doesn't have the sense to be terrified. She just looks at Natasha, seeming almost amused.

When no reply seems forthcoming, Natasha continues. "You poisoned my companion." Idly, Natasha picks up one of the store's gifts cards and reads the slogan ordering her to have a Merry Christmas.

"I didn't realize you would figure it out," the woman speaks for the first time, features taut. Perhaps she has more sense than Natasha realized. "He's stronger than I thought."

"He tends to be underestimated," Natasha agrees easily, despite the foreboding looming over her. "Like you, I imagine."

A smile is what Natasha is given, a smile full of deadly promise.

Natasha drops the gift card on the counter between them, meeting the woman's eyes. Natasha's new target flinches, whitening as Natasha returns her smile.

"You will give me the antidote," Natasha tells her. "My companion will recover."

"Why-"

Until now, Natasha never faced the realization of how much her time in SHIELD changed her. Now, with revulsion over what she's willing to do hitting her, the difference surprises her.

Smile widening, she interrupts the woman once more.

"You'll find I have methods of persuasion."

* * *

Natasha reenters the apartment, knocking once on the door before entering. Steve's tipped over, gun cradled within one hand as he sleeps.

His skin's raging hot and slick to the touch as Natasha's steady hands pull his shirt off. Carefully, she lines the needle up with his heart, slipping it through his skin before she begins to depress the plunger.

He doesn't flinch as the serum enters his body, doesn't flinch as the needle splits skin. Instead, he remains as still as death as Natasha pulls away. Natasha sets the syringe gently on the side table before reaching for her phone.

"Hill," she says quietly. "Targets have been neutralized. Rogers is in recovery."

"Do we need to send agents for pick up?"

Natasha hesitates, letting herself feel a moment of regret. "Yes," she says after a long moment. "Two for detainment in custody. When will they arrive?"

"The situation with Stark has been resolved," Hill tells her almost cheerfully. "We can have pickup ready in thirty six hours."

"I look forward to it," Natasha folds her legs under her, glancing at the clock as it turns to midnight. "Merry Christmas, Agent Hill."

She can almost hear the smile in Maria Hill's voice as the reply comes. "Merry Christmas, Agent."

* * *

Natasha sits like that for the rest of the night, half dozing beside Steve as she monitors him. It takes another hour for his fever to break, but as his breathing begins to smooth, a rush of relief fills her.

Natasha doesn't like working with variables. She's always been a solo operative, always relied on no other but herself.

Except now, as she listens to her teammate's unconsciousness turn into genuine sleep, she can't help but smile. If dealing with the anxiety, the uncertainty of the future is her price to pay for this, then she will gladly accept it. Natasha, for the first time since Steve began to fall ill, lets herself yawn. She can admit she's exhausted, can admit that she's bone weary and ready for sleep, but it doesn't matter at all.

She can keep watch for a few more hours, yet.

* * *

Happy New Year, everyone! Thanks so much to all of you who have faved, followed, reviewed, and read my works.

-V


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